fix(oidc): prompts slice conversion function returns slice which contains unexpected empty strings (#8997)

# Which Problems Are Solved

Slice initialized with a fixed length instead of capacity, this leads to
unexpected results when calling the append function.

# How the Problems Are Solved

fixed slice initialization, slice is initialized with zero length and
with capacity of function's argument

# Additional Changes

test case added

# Additional Context
none

Co-authored-by: Kolokhanin Roman <zuzmic@gmail.com>
Co-authored-by: Tim Möhlmann <tim+github@zitadel.com>

internal/api/oidc/auth_request_converter.go

@@ -158,7 +158,7 @@ func IpFromContext(ctx context.Context) net.IP {
 }
 
 func PromptToBusiness(oidcPrompt []string) []domain.Prompt {
-	prompts := make([]domain.Prompt, len(oidcPrompt))
+	prompts := make([]domain.Prompt, 0, len(oidcPrompt))
 	for _, oidcPrompt := range oidcPrompt {
 		switch oidcPrompt {
 		case oidc.PromptNone: